Thank you for the reply!

I am creating it in a third world country for mainly rural folks. I see in OpenTok they have the following bandwidth requirement:

Video: 300 kbps per stream (recommended lowest level)

Audio: 50 kbps per stream (recommended lowest level)

I guess it's in bytes. Here, average speed is around 64kbps/512Kbps. Is there anything else which have further low requirement? For hangout it's pretty low:

https://support.google.com/plus/answer/2979333?hl=en

Something in this range would be best.